The present invention relates to high denier per filament and low total denier cellulose acetate tow bands and smoking device filters produced therefrom.
The draw resistance of other smoking articles, e.g., cigarettes, is a major determinant of the draw characteristic(s) of the cigarette which are experienced by a smoker. In cellulose acetate filters, draw characteristics may depend on several factors including the cellulose acetate filament characteristics, the amount of cellulose acetate filaments, and the concentration of additives incorporated in said filaments. One measure of draw characteristics is the encapsulated pressure drop. As used herein, the term “encapsulated pressure drop” or “EPD” refers to the static pressure difference between the two ends of a specimen when it is traversed by an air flow under steady conditions when the volume flow is 17.5 ml/sec at the output end when the specimen is completely encapsulated in a measuring device so that no air can pass through the wrapping. EPD has been measured herein under the CORESTA (“Cooperation Centre for Scientific Research Relative to Tobacco”) Recommended Method No. 41, dated June 2007. Higher EPD values translate to the smoker having to draw on a smoking device with greater force.
Currently, the desired draw resistance for cellulose acetate filters is achieved by forming filters from tow bands having low denier per filament (dpf) and high total denier, i.e., lots of filaments each with a small cross-sectional area. The small cross-sectional area is believe to provide high surface area, which translates to higher filtering efficacy.
However, these low dpf, high total denier tow bands have issues when responding to markets that are trending to smaller-diameter smoking articles and jurisdictions having increasing regulations that require increased filter efficacy. First, producing smaller diameter smoking articles with these known tow bands effectively condenses the filaments into a smaller space, which increases the EPD and changes the draw characteristics as a result. Second, increasing the filter efficacy of the high total denier of these tow bands would require more surface area, e.g., more filaments, which would exacerbated the higher EPD issue. Additionally, the inclusion of particles that actively remove smoke components from a smoke screen (e.g., carbon) fill the voids of the filters leading to higher EPDs.
Therefore, among other things, a need exists for tow bands capable of producing filters that can respond to market trends for smaller diameter cigarettes, e.g., about 17 mm circumference or less, and increasing jurisdictional regulations while maintaining the draw characteristics appealing to smokers.